A disk playback apparatus using a disk recording medium has been known as such an electronic apparatus for recording and/or playing back an audio signal and a video signal.
As shown in FIGS. 1 and 2, such a known disk playback apparatus 100 has a housing 101 serving as a main body thereof The housing 101 has a rectangular block shape comprising a top panel 102 forming the top side thereof, a bottom panel 103 forming the bottom side thereof, a front panel 104 forming the front side thereof, a back panel 105 forming the back side thereof, and two, left and right, side panels 106 and 107 forming the left and right sides thereof More particularly, the housing 101 is shaped by assembling with any two opposite sides arranged parallel to each other; the top panel 102 and the bottom panel 103, the front panel 104 and the back panel 105, and the left panel 106 and the right panel 107.
A support leg 108 made of a vibration absorbing material such as rubber is mounted to each corner of the bottom panel 103 of the housing 101. The housing 101 is placed with its support legs 108 directly on a platform 109 such as a table or a bed.
A first circuit board 111 and a second circuit board 112 serving as a playback unit and a signal processor of the disk playback apparatus 100 are installed in the housing 101. The circuit boards 111 and 112 are shaped of a flat sheet-like form which is made of a synthetic resin material having a degree of rigidity and located in the housing 101 so as to extend in parallel to both the top panel 102 and the bottom panel 103.
Also, a disk rotating mechanism 113 for rotating the recording medium or an optical disk 99 of the disk playback apparatus 100 is mounted in the housing 101. The disk rotating mechanism 113 has a spindle motor 114 and a disk table 116 mounted to the distal end of a spindle 115 of the spindle motor 114, as shown in FIG. 1. The disk rotating mechanism 113 is secured with its spindle motor 114 fixedly joined to a base 117 in the housing 101. In particular, the spindle motor 114 is anchored to the base 117 so that its spindle 115 extends vertical to the top panel 102 and the bottom panel 103 which are arranged parallel to each other. The disk table 116 on which the optical disk 99 is loaded is mounted to the distal end of the spindle 115 so that its optical disk 99 loading surface is vertical to the spindle 115 and it can rotate together with the optical disk 99.
Since the loading surface of the disk table 116 extends vertical to the spindle 115, the optical disk 99 when loaded on the disk table 116 is supported at its main side parallel to the top panel 102 and the bottom panel 103.
As not shown, a loudspeaker unit for playing back the audio signal read out from the optical disk 99 to emit acoustic sound is also installed in the housing 101.
The disk playback apparatus 100 having the foregoing arrangement is placed with its support legs 108, mounted to the bottom panel 103 of the housing 101, directly on the platform 109 and during the playback action, its housing 101 receives external acoustic power or vibration from the platform 109 or the ambient space. The vibration received from the platform 109 may be attenuated by the support legs 108 made of the vibration absorbing material and prevented from direct propagation to the housing 101 itself and the inside of the housing 101. However, the external acoustic power or vibration from the ambient space is directly transmitted to the housing 101 of the apparatus and produces a significant of vibration on the housing 101.
Also, the disk rotating mechanism 113 in the disk playback apparatus 100 generates vibration when it starts driving. The vibration from the disk rotating mechanism 113 is transmitted via the base 117 to and vibrates the first circuit board 111 and the second circuit board 112. Moreover, the sound emitted from the loudspeaker unit propagates to and vibrates the first circuit board 111 and the second circuit board 112.
In the conventional disk playback apparatus 100 as an electronic apparatus, the top panel 102 and the bottom panel 103 of the housing 101 facing each other extend parallel to each other while the first 111 and the second circuit board 112 in the housing 101 are arranged parallel to both the top panel 102 and the bottom panel 103. This causes the vibration generated on the top panel 102, the bottom panel 103, and the two circuit boards 111 and 112 to repeat reflection between the top panel 102 and the first circuit board 111, between the bottom panel 103 and the second circuit board 112, and between the first circuit board 111 and the second circuit board 112, as denoted by the arrow in FIG. 1, thus creating unwanted resonance between the top panel 102 and each of the two circuit boards 111 and 112 and between the bottom panel 103 and each of the two circuit boards 111 and 112. The resonance will then trigger excessive vibration on the top panel 102, the bottom panel 103, and the first circuit board 111 and the second circuit board 112 of which the amplitude is greater than that of the original vibration generated in the housing 101 or of the external vibration introduced to the housing 101.
The support legs 108 of the disk playback apparatus 100 are identical in height. While the disk playback apparatus 100 is placed with its support legs 108 directly on the platform 109, its bottom panel 103 becomes parallel to the platform 109. This causes the vibration derived from the bottom panel 103 or the platform 109 to repeat reflection between the bottom panel 103 and the platform 109, as denoted by the arrow in FIG. 1, hence creating a significant resonance between the bottom panel 103 and the platform 109. Accordingly, the resonance will trigger excessive vibration on the bottom panel 103 of which the amplitude is greater than that of the external vibration introduced to the bottom panel 103. The excessive vibration on the bottom panel 103 repeats reflection between the first circuit board 111 and the second circuit board 112 and produces greater resonance which then vibrates the two circuit boards 111 and 112 to a higher amplitude.
The excessive vibration on the two circuit boards 111 and 112 and thus electronic components of the circuit boards 111 and 112 impairs the action of the signal processor unit on the circuit boards 111 and 112. Particularly in the disk playback apparatus as an electronic apparatus, the audio or video signal read out from an optical disk may be added with unwanted noise components caused by the vibration and its properties will be declined in the playback.